/Engine/Source/Runtime/Engine/Public/GPUSortManager.h
Register a client system into the sort manager. Client systems are systems that will callAddTask(). Those systems need to register a callback, the possible used flags for their tasks and a name. The callback is required because the initial content to perform GPU sorts is only configured long afterAddTask()gets called in the rendering loop.
void Register ( const FGPUSortKeyGenDelegate & CallbackDelegate, EGPUSortFlags UsedFlags, const [FName](API\Runtime\Core\UObject\FName) & InName )